It's a good pricing model which benefits both ends. A SaaS option for people that don't want to bother with technical stuff is a good idea.
I've created the checkout/licensing and renewal myself because of the flexibility and not depending on other external companies. The licensing system is quite simple, the software doesn't ask for license verification at the moment. The system will allow the downloads based on the license the user selects. The license system is integrated with BitBucket. On each release BitBucket sends a POST request to a secure endpoint with a prepared ZIP file containing the app files. On each release, a new entry is created on the licensing system indicating the version and other details. Licenses are tied to the major release version number (e.g., "1" in v1.2.0). When v2.0.0 is released, new licenses are tied to the v2. Users will only have access to minor and patches releases until a renewal is made. That's a brief description of how the system works.
For the checkout, I've created two Laravel packages (currently private) for sale statements (quotes, orders, invoices, etc) and another package for the affiliate program. I'll be releasing them with MIT license on GitHub.
Sure! Feel free to send me a PM on Twitter @gerardojbaez or an email to g[at]gerardobaez.com. I'll be happy to help.